Saturday, October 30, 2021

Pine Creek Loses some of its Forest


Malden Post Office before the fire

Attribution of a single wildfire event to global warming is confounded by lots of other factors. The Malden area and Pine Creek valley are located in a climate edge area where pine forests meet grass lands (and now dry land wheat fields) in a mosaic landscape. Pine Valley where Malden is located was already in a fire prone area. Every summer the area becomes dry enough to burn with the grasses and brush being susceptible for a longer period and the trees for a shorter period. Towards the southwest that length of time becomes longer and to the north and east the length of time is shorter. Pine Valley is in a boundary area just moist enough that tree killing fires have been infrequent enough such that the valley has significant forest stands. 

With warmer average temperatures the length of time the area is susceptible to fire is now longer. But other factors can increase fire risk - years of fire suppression and changes to land use also alter the fire risk and how a fire will behave. With lots of roads, fires in Pine Valley could be readily suppressed and put out as long as fire weather conditions were not severe. Land use changes also play a role. Over time the forested areas began to encroach into the Malden town site.

The weather event associated with this fire included very high winds associated with an Arctic cold front that surged across the area from the northeast. The high winds had followed several days of at or near record daily highs in the region. The weather set up and fire risk was predicted several days before it took place (Inland Northwest Weather.blogspot). The same weather event was also associated with a much large fire that burned over 60 miles in the Okanogan Valley as well as the very intense wildfires on the west slopes of the Oregon Cascades.   

Pre and post fire aerial images show that a fair bit of the forests that were in the Pine Creek valley burned during the fire. 

Malden 1954

Malden 2017

Malden 2021

Northeast of Malden 2017

Northeast of Malden 2021

Pine City 2017

Pine City 2021

Sunday, October 10, 2021

Malden, Washington Notes: Ice Age Flood Route

A bit over a year ago a wildfire burned much of Malden, Washington. Due to the extent of the destruction, the already tenuous economy of the small town and the very delayed National Major Disaster Declaration by the President, there have been follow up stories and takes on the fire and the aftermath ( Northwest Public Radio and Spokesman Review as well as Spokane area TV stations have continued to report on the town's effort at recovery.  

Malden Post Office before the fire

Malden is a bit off the usual routes; hence, I thought a little background on the landscape of Malden and the vicinity would be of use. I passed through Malden about a month before the fire and also on a trip to Rock Creek and Bonnie Lake (bonnie-lake-precambrian-schist). On that earlier trip I paused at the Post office (above picture). 

Malden is located in Pine Creek valley in the norther part of the Palouse. J Harlen Bretz (1923) recognized that the Pine Creek valley was a pre existing valley that was further eroded by ice age floods, "The valley during this episode in its history was but a channel. The glacial stream filled it from side to side for a depth of tens of feet. This is shown a few miles above Malden, where the stream flooded over a low shoulder of basalt, cutting a channel in the rock at least 40 feet deep, though the main valley alongside was a wide open and received gravel deposits." 

Map of Spokane Flood routes from Bretz (1925)

Flood water spillway from upper Latah Creek into the North Fork of Pine Creek (Bretz, 1923)

The ice age floods that Bretz was describing were the result of water spilling over from Latah Creek. The Okanogan ice lobe dammed the Columbia River forming glacial Lake Columbia in the backed up the Columbia River. The lake extended up the Spokane River and Latah Creek, a tributary stream to the Spokane River. When the ice dam at that formed ice age Lake Missoula collapsed, the flood waters surged out of the rapidly draining lake and into the Spokane area and into Lake Columbia. The sudden influx of a massive surge of water resulted in Lake Columbia overtopping at numerous low divides to the south. One big spill way is the Cheney-Palouse scabland tract southwest of Spokane. Interstate 90 passes through part of the tract. But some water backed up Latah Creek and spilled over a divide into the Pine Creek Valley.  

DEM of spillway from Latah Creek into Pine Creek

The ice age flood features in Pine Creek are a bit more subtle than the raw wide stripping of soil that took place in the very broad Cheney-Palouse route. But the features were noticeable to Bretz and are not consistent with the other valleys that were not flood routes that pass through the Palouse landscape. 

Another factor that softens the flood features in the Pine Creek Valley is that this flood route has a bit wetter climate than those to the west and the valley has more areas of pine -- hence the name Pine Creek. More on that on a future post.